Impregnated coil and method of making the same.



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To all whom it mag concern: Y a v Be it known that I, Lno H. BAEKELAND,a. citizen of the United States, residing at Yonkers, in the county ofWestchester and State of New York, have invented certam new and usefulImprovements in lmpregr nated Coils and Methods of Making the Same, ofwhich the following is a specification. .r i

, The object of this invention is the provision of an electricalconductor in the form of a coil or equivalent structure, whereof the Iwindings are embedded in and supported by aninfusible and insolubleorganic body.

According to the invention I .producethroughout the mass of the coilsorwindings of dynamos, motors, transformers and other electrical devices,a synthet1c condensatlon product of phenols and formaldehyde, thiscondensation productservi'ng not only as an insulator for the windingsbut as an eflicient and durable support therefor. Owing to theinfusibility of the supporting coils are enabled to endure,.without inury, a far greater degree of overload than is the case where fusible orresinous roducts are used; and owing to the insolu ilit of the .mass, itmay be directly immerse in oil,

and may be used under conditions involving exposure to water-'or'steam,to acid or alkaline liquids, or to organic or inorganic'sol- I vents,without injury.

v For a full understanding of my invention I'will describe a preferredmethod of carrying the same into effect. v

Phenol or its homologues is mixed with-formaldehyde in approximatelyequal molecular proportions, with -.or without the addition smallproportions of catalytic or conof densing agents, and the'mixture isheated, preferably in a vessel provided with a return condenserr Aftersome time, depending upon the temperature and the proportion ofcondensing agents used, the mixture separates into two layers, the oneaqueous and the other oily .or viscous; the latter represents the firstreaction products .and 1s hereinafter referred to as the initial.con-'densationproduct. This initial condensa- .tion product is soluble inalcohol, acetone,

phenol andother solvents, but isonly imperfectly and partially solublein benzol. If

, sufliciently cooled it may :becomepasty or mass, such stifl',", andsometimes brittle, but islrea dily liquefied byv application pfheat,andin its fluid and mobile condition ossesses excel lent penetrative owers,an readily pene-, trates. not only t e coil-interstices, but also thefibrouscoating of the coils, ifsuch be used. If subjected tosufiiciently prolonged heating under proper, conditions it isvfinallytransformed into a hard condensation product, which is insoluble inalcohol, acetone, phenol orv glycerin, and remains hard attemperaturesbelow300 C.;-at higher temperatures it does not fuse,although some carbonization may occur. a This material isa solid,homogeneous, impervious, infusible,

and insoluble-body which possesses excellent insulating properties; andis hereinafter referred tov as the final condensation product. Thisfinal condensation product presents many advantages as compared withhard rubber, and other insulators as heretofore fused. ,In'particular,it may be mentioned that -it is capable of withstanding temperatures atwhich hard rubber ,would be entirely destroyed, so that coilsimpregnated therewith can withstand a very heavy overload withoutinjury. Furthermore, it

does not fuse at any temperature, although as above stated, carbomzationmay take place when'it is excessively heated. It possesses the importantadvantage, as compared with hard rubber, that it is free from sulfur,

which is well known to exert a strong corrosive action upon copper,particularly at temperatures considerably above normal,

:and is also known to'give rise under. the oxidizing effects of air and1 light to disturbing traces of sulfuric acid.

The initial condensation product prepared as described above maycontain-some .free

wateraor other volatile constituents, and it is advisable to expel theseby heat before transforming it into thefinal condensation product. Suchheating should preferably be effected under reduced pressure and at lowtemperatures in order to avoid premature conversion with loss ofmobility. The liquid condensation product is then applied to the coil insuch manneras completely to impregnate the same, the impregnation beingassisted,. if necessary, by the application of increased pressure, or ofvacuum. For the purpose of such impregnation, the initial,

or impregnated with the initial condensation f condensation product maybe used alone or in admixture with other substances suchas fillings andthe like; or it may be applied in mixture with. ma-

asbes'tos, insulating terials ada ted to facilitate the coating or thesubseq ent hardening operation or to msure proper flexibility of thefinal coating.

' If desired the. conductors may be reviously coated with cotton, silk,asbestos, insulatin varnishes or the like, which are then coate product.The coated conductor, coil or other construction is then subjected to ahardenc this is a slow and very uncertain 1 tion of heat, may

foaming and to msure homogeneous hard-' ing operation to transform theinitial condensationmroduetinto aiinal infusible and insolublecondensation product havin the properties-above described. Although 1nthe case of thin insulating layers this may be accomplished by simpleheating especially such an irregular way as to destroy its homog'eneity,rendering it porous or cellular in character, and greatly impairing itsvalue as an insulator. In certain cases as when the coil orotherconstruction is closed or is covered by an external layer or envelop, orcasing, the internal pressure developed by the volatile constituentsliberated under the acbe sufiicient to prevent ening, but it is usuallydesirable or necessary to maintainv during the heating or hardeningprocess, an appropriate external pressure, as for instance by conductingthe hardening operationiin hermetically closed chambers, or envelops,heat being applied in any suitable manner and the temperature beingmaintained preferably between 120 and 200 C. The pressure may. beapplied by means of compressed air or by a compressed -inert gas;'in thelatter case superficial oxidation' of the coating is avoided. As an al-lternative method the coating maybe hardened while immersed in an inertliquid maintained under pressure; the liquid hydrocarbons or mineraloils being particularly suitedfor this purpose. In this and'in all othercases the hardening may be conveniently effected by passing through theconductor an electric current sufiicient to heat the coating to thedesired'tem'perature and for-a suflicient period of time. This hardeningmay be re garded, from a chemical point of view, as an efiect due to thepolymerization of the initial ing by and during the act ofpolymerization the qualities of infusibility and insolubility.-

I am aware that it has been proposed to V cm loy for insulating purposesa plastic b0 y made by boiling together phenol and formalhehydewithforty to eighty per cent. of sulfuric acid having a concentration of16to 17 B., and 'I' do not claim such process, which is entirelyinapplicable to the impregnation of coils. In the first place,

a product thus prepared persistently retains free acid, which wouldrender itinap licable for my purposes, and in the secon place, a plasticbody ofw'the character described cannot be used under any conditions forpurposes of impregnation. According to the present process there isfirst produced a liquid or readily-liquefiable, mobile condensationproduct which is applied to the impregnation of coils; and this mobileproduct is'thereafter submitted to heat under such conditions aswillresult in its transformation, in situ, by;a process ofpolymerization, into a solid, compact homogeneous and hi hly inertsupport for the windings.

he term phenol employed in the claims is to be understood as includingthe homologues of phenol, such as cresol, and the term formaldehyde istobe understood as includmg the polymers and equivalents offormaldehyde.

An organic insulating composition adapted for coil impregnation isclaimed in my divisional application Serial, No. 879,946,

'- filed December 31, 1914.

I claim: 4 I

1.. The method of making coils for electrical uses, which consists informing a coil having its windings in spaced relation, filling theinterstices between the windings with a fluid-and mobile phenoliccondensation product, and then transforming said productyin sitminto asolid, homogeneous,

impervious, insoluble, and infusible body,

servingboth as a support and as an insulator for said windings.

2. The method of makingcoilsfor electrical uses, which consists informinga coil havin its windings in spaced relation, fill;

ing -t e interstices between the windings with a fluid and mobilephenolic condensation product combined'with a substance capable ofincreasing the flexibility of the final ings and simultaneouslyimpregnating said 'product', and then transformingsaid product, in situ,into a solid, homo ene us, impernolic condensation product, and thentransforming said product, in. situ, into a. solid, homogeneous,impervious, insoluble, and infusible body, serving both as a support andas an insulator for said windings.

4. The method of making coils for electrical uses, which consists informing a coil having its windings in spaced relation, said windingsprovided with a fibrous covering,

filling the intersticesbetween said windings and simultaneouslyimpregnating said fibrous covering with a fluid and mobile phenoliccondensation product combined with a substance capable of increasing theflexibility of the final product, and then transforming said product, insitu, into .a solid, homogeneous, impervious, insoluble and infusiblebody, serving both as a support and as an insulator for said windings.

5. As a new article of manufacture, a coil for electrical uses whereofthe windings are both separated and insulated by a solid, homogeneous,impervious, insoluble, and infusible phenolic condensation product, saidcondensation product serving both as a support and as an insulator forthe coil windings.

6. for electrical useswhereof the windings are both supported andinsulated b a solid, homogeneous, impervious, insolub e, and infusiblephenolic condensation product, com bined with a substance ca able ofincreasing its flexibility, said con ensation product serving both as aI support and as an insulator for the coil win in 7 As a new article oinanufacture, a coil for electrical uses whereof the windings are bothseparated and insulated by a solid, 7 homogeneous, impervious,insoluble, and infusible phenolic condensation product, sub- As a newarticle of manufacture, a coil stantially free from water or volatileconstituents, or acid-reacting components, said condensation'productserving both as a support and as an insulator for the coil wind- -As anew article of manufacture, a boil for electrical uses whereof the winare both separated and insulatedby a solid, homogeneous, impervious,insoluble, and infusible phenoliccondensation product, substantiallyfree from water; or volatile constituents, or acid-reacting components,but combined with a substance capable of increasing its flexibility,said condensation product serving both as a support and as an insulatorfor the coilwindings.

9. As 'a new article of'manufactu're, a coil for electrical uses whereofthe windings are provided with a fibrouscovering, and are both separatedand insulated by a solid, homogeneous, impervious, insoluble,and'infusible phenolic condensation product, said condensation productserving, both as a support and as an insulator for the coil windings.

10; As a new article of manufacture, a coil for electrical uses whereofthe windings are provided with a fibrous covering, and are bothsupported and insulated by a solid, homogeneous, impervious, insoluble,and infusible phenolic condensation product, combined with a substancecapable of increasing its flexibility, said condensation productservingIboth as a support and as an insulator for the coil win Intestimony whereog l aflix my signature in presence of two witnesses.

' LEO H. BAEKELAND;

I witnfissesszT Mhmi' E. Sonommo.

